Analysis Methods and Seismic Strengthening of Existing Masonry Arch Bridges of the Conventional Railway Network

In compliance with the Italian law OPCM 3274/2003 (Ordinance of Presidency of the Council of Ministers No. 3274, 2003) the seismic vulnerability of about 5600 bridges is currently being assessed by RFI (Italian Infrastructure Manager). Masonry arch bridges represent a significant part of the railway bridge population. From 1830 to 1920 all Italian railway bridges were built with this project solution. This work presents the mitigation of the seismic risk process about masonry arch bridges of the Italian railway network. The process includes an initial phase of geotechnical and structural investigations, used to evaluate the minimum risk indicator among all the possible collapse mechanisms of each bridge, by specific analyses. In particular, the structural capacity is assessed by kinematic analyses for simple single span bridges otherwise by pushover analyses applied to 3D FEM models. After that, for those structures that show a lower structural capacity than the seismic demand defined by the Italian standards, the seismic improvement intervention is designed, considering the usage requirements of the Infrastructure.